Dr. Siddall is an outdoor enthusiast, author, and activist. He has traveled widely and enjoys sharing his adventures with the public.
I stopped to fill up my gas tank at Billy Blankenship’s general store in Pennsylvania on the way to a trailhead on the Appalachian Trail . The elderly attendant dressed in worn coveralls and a faded Steelers cap, stepped outside to chat. I took the opportunity to ask if he had heard the weather forecast. His response was classic “ I never pay attention to forecasts. If the weather is nice, I stay out. If it's stormy, I stay in.” At the time, I thought his response was just an example of mountain humor. However, I have since learned that “Billy’s Rule” was a wise summation of the art of weather forecasting.
History of Weather Forecasting
As long as humans have traveled the earth, the need to predict the weather has been critical to their survival, as they searched for food, water, and shelter. Early humans relied on the lore of naturalistic observations of the environment passed on by their elders. Since the 19th century, weather prediction has been based on the ability to monitor and analyze atmospheric factors such as cloud formations, wind speed and direction, temperature, humidity, and barometric pressure. Current weather forecasting science employs orbiting satellites and computer based models that are capable of continuous observation and assessment of numerous weather variables. In spite of these technological improvements, the complex nature of weather dynamics makes forecasting challenging.
Accuracy of Weather Forecasting
According to the National Oceanic and Atmospheric Administration in 2021 a seven-day forecast can accurately predict the weather about 80 percent of the time and a five-day forecast can accurately predict the weather approximately 90 percent of the time. However, from my experience, forecasts of over a few days are seldom viable in terms of practical accuracy as a hiker moves through the landscape. In spite of the variability of weather forecasts, it is wise to consider the most dependable meteorological principle referred to as “persistence forecasting” which posits that whatever the weather is today, will likely continue tomorrow.
By learning to use your five senses (taste, smell, touch, hearing, sight) you can make direct observations of many common atmospheric variables to forecast the weather, For example, you can learn to identify cloud formations associated with fair and inclement weather, gauge wind speed and direction on the surface of your skin and estimate changes in the air’s humidity and barometric pressure.
Observations of natural phenomena also have weather forecasting value and have been used for centuries by native peoples, explorers and farmers. Some useful examples include the following:
- High wispy clouds are associated with fair weather
- Towering, dense or dark clouds suggest impending stormy weather especially if the wind is blowing toward you
- Birds fly high in the sky during periods of high pressure and lower to the ground before a storm
- Campfire smoke rises with high pressure and settles toward the ground when the pressure drops
- In fair weather, tree leaves show their normal orientation but show their undersides when the air pressure drops.
- Many people report having a heightened sense of smell when rain approaches and increased sensations of pain in their joints or sinuses during periods of low pressure.
In 1643, Evangelista Torricelli, an Italian physicist and mathematician, and a student of Galileo, was credited with inventing the barometer which quantifies the measurement of air pressure. This important invention ushered in the era of scientific weather forecasting. Modern barometers have now been incorporated into smartphones and watches available to hikers.
Barometric pressure is the measure of the weight of the atmosphere pressing down on the earth's surface. Increased pressure pushes air down. As air moves down and warms, the formation of clouds and storms dissipate. High pressure typically signifies fair weather, particularly if the barometer registers a stable high pressure reading.
When barometric pressure drops, this means air can rise and cool increasing cloud formation and precipitation. When a barometer registers a drop in pressure, inclement weather typically follows.
Dramatic changes in air pressure are associated with more rapid changes in the atmosphere. If pressure suddenly drops, expect storms or precipitation. Air pressure that rises and stabilizes, is associated with fair weather.
For a review of basic weather forecasting, I recommend two books: Guide to Weather Forecasting: All the Information You'll Need to Make Your Own Weather Forecast by Steve Dunlop, 2008 and The Secret World of Weather: How to Read Signs in Every Cloud, Breeze, Hill, Street, Plant, Animal, and Dewdrop by Tristan Cooley 2021.
Weather Forecasting Apps
The website Forecast Adviser ranks weather sites based on their accuracy including Accuweather, AerisWeather, Foreca, and the National Weather Service. You can type in your zip-code to find the most accurate weather site based on your location.
Internet apps such as The Weather Channel's free, ad-supported weather app is available for Android and iOS platforms. This app provides users with a variety of useful meteorological data such as temperature, wind and visibility on an hourly or daily basis. Also included is an extended 10-day forecast. Interactive maps provide the latest Doppler radar data and severe weather alerts. The Weather Channel also allows users to share. upload images, tweets, videos and photos.
Weather Hazards and Precautions
Weather is subject to change and can be unforgiving for the underprepared. Before setting out on a hike, familiarize yourself with the climate and terrain of your proposed route and gear up for a worst case scenario. Be prepared for typical weather hazards including hypothermia, hyperthermia, dehydration and lightning.
Hypothermia or overheating occurs when your body loses heat faster than it produces it. The most common cause of hypothermia is exposure to cold weather or cold water. Protection against hypothermia includes warm layers of clothing, emergency shelter and the ability to create a fire.
Hyperthermia or an abnormally high body temperature occurs most commonly from physical exercise in a hot, humid environment. Protection from hyperthermia includes wicking clothing, a wide brimmed hat or sun hoodie, sunscreen, an adequate water supply, water filter, and electrolyte supplements and snacks.
When hikers experience hyperthermia they should stop all physical activity, move to a shaded area, loosen heavy clothing, rest and rehydrate by drinking a beverage supplemented with electrolytes. Hikers can also benefit from consuming snacks that are sweet and salty.
Dehydration occurs when your body loses excessive water through perspiration in warm and humid weather which is not being replenished by drinking normally. Symptoms can range from headache and decreased urine output to debilitating organ failure and shock. Prevention involves drinking water regularly and resting in the shade on regular intervals. Normal hydration is associated with a normal frequency of urination that is light yellow in color. Hikers should carry at least two liters of water depending on the terrain and the heat.
Lightning is present in all thunderstorms which are most active during the summer’s prime hiking period. Although only 10% of lightning strikes hit the ground, its lethal power can cause serious injury or death.The National Weather Service reports about 300 people are injured and 50 people die annually after being struck by lightning.
If a thunderstorm is threatening. head for lower ground and avoid prominent topographic features such as lone tall trees, shallow caves or overhangs, water, and metal objects such as pack frames, trekking poles, and metal gear. Seek shelter in an enclosed structure, car, low stand of trees or low area in an open field or meadow.
If you are caught in a thunderstorm with lightning, make yourself as small as possible by getting into the lightning safety position by crouching down on the balls of your feet, tuck your head as low as you can, and cover your eyes and ears. Minimize your contact with the ground by squatting on insulated material such as your sleeping pad. Distance yourself 20 to 100 feet from all other people in your hiking group. Wait for up to 30 minutes until the storm passes.
In the event that lightning strikes a hiker, check to see if the victim is breathing and has a heartbeat. Check for a pulse at the carotid artery, on the neck directly below the jaw. If the victim does not have a pulse start cardiac compressions. If the victim is not breathing, also start mouth-to-mouth resuscitation. Continue CPR until help arrives. If the area is cold and wet, use a protective layer between the victim and the ground to decrease hypothermia. Lightning may also cause other injuries such as burns, shock, and other physical trauma. Treat these injuries with basic first aid until help arrives. Unless necessary, do not move victims who are bleeding or have broken bones.
In addition to standard hiking gear, the following items should be carried to address weather emergencies.
- Clothing: layered-wicking fabrics
- Rain/weather gear, emergency shelter
- Sun screen, a wide brimmed hat or weather hoodie
- Warm toboggan, insulated jacket, gloves
- Water, filter, electrolyte supplements
- Fire starter
- Sweet and salty snacks
- First aid kit
Weather forecasting is challenging and can be unforgiving for the underprepared. Scientific and naturalistic forecasting are reviewed. The wise hiker will gear up for a worst case scenario and be prepared for typical weather hazards including hypothermia, hyperthermia, dehydration and lightning.
Quick Guide to Weather Forecasting
- Stable weather: barometric pressure steady, minimal changes in clouds, wind, or temperature
- Fair weather: barometric pressure rising, clear skies, high wispy clouds light breeze, warming temperature,
- Changing weather: barometric pressure decreasing, clouds forming, wind increasing, temperature dropping
- Inclement weather: barometric pressure falling, dark clouds forming, wind may be gusty followed by a temporary calm, cooling temperature. A rapid drop in the rate of barometric pressure suggests a storm is imminent.
This content is for informational purposes only and does not substitute for formal and individualized diagnosis, prognosis, treatment, prescription, and/or dietary advice from a licensed medical professional. Do not stop or alter your current course of treatment. If pregnant or nursing, consult with a qualified provider on an individual basis. Seek immediate help if you are experiencing a medical emergency.
© 2022 James W Siddall